FR2463032A1 - IMPROVEMENTS TO HYDRAULIC ANTI-PUSH BRAKING SYSTEMS FOR VEHICLES - Google Patents

Abstract

INVENTION CONCERNING VEHICLE BRAKING. A HYDRAULIC ANTI-SLIP SYSTEM COMPRISING A PUMP HAVING A SET OF PISTONS, WHICH INCLUDES A Plunger 16, 17 TAKEN A RACK AND FORT MOVEMENT IN A DRILLING BY MEANS OF A DRIVE MECHANISM 20, A SIGNAL PISTON 25, 26 COUPLED TO THE Plunger AND A SPRING 37, 38 REQUESTING THIS Plunger TO DISCOME FROM THE DRIVE MECHANISM. THE SIGNAL PISTON PRESENTS AN AREA EXPOSED TO THE PRESSURE OF A MASTER CYLINDER 43 OR THE BRAKE WHEN THE BRAKE IS APPLIED TO SORRY THE SIGNAL PISTON IN A DIRECTION SUCH THAT THE DIVERS CAN COUPLE TO THE DRIVE MECHANISM. WE PROVIDE A DISCHARGE VALVE 8, 9, 10, NORMALLY CLOSED, WHICH CONTROLS, IN A STOPPING CHAMBER 59, 61, THE FLUID TO WHICH THE PISTON ASSEMBLY IS EXPOSED AT LEAST AFTER APPLICATION OF THE BRAKE, AND REGULATES IT. EXHAUST FOR COUPLING THE PLUNGER AND THE DRIVE MECHANISM. APPLICATION TO THE PRODUCTION OF HYDRAULIC BRAKES IN WHICH THE PUMP ONLY WORKS DURING SHORT PERIODS OF CORRECTION OF SLIP.

Description

The present invention, concerning the braking of vehicles, is more

specifically relating to

  anti-skid hydraulic brake systems for vehicles

  Such devices, of the kind in which the actuation fluid supply of a vehicle brake from a suitable source is modulated according to

  slip provided by a slip detection means.

  Some known systems opposed to slippage and of the type exposed include a pump which is driven substantially continuously to draw off

  fluid from a tank and return it to it after circulating

  in a closed circuit. Normally a modulator assembly maintains an open brake valve between the power source and the brake and, when a slippage signal is active, the flow of the pump is restricted to actuate the modulator assembly, first allowing to the brake valve to close, then releasing the pressure applied to the brake. Alternatively, the brake fluid is discharged in case of slippage and the pump acts to pump back the volume of the discharged fluid to use it for the reapplication of the brake at the end of the slip signal. According to the invention, a system of

  hydraulic anti-skid braking of the kind exhibited

  takes a pump that has a set of pistons (this set of pistons including a pump plunger that can move back and forth in a bore by means of a drive mechanism), a signal piston which is coupled to the pump plunger and resilient means for biasing the pump plunger to disengage from the drive mechanism, the signal plunger having a first area exposed to pressure from the power source or the brake when the latter is applied for solicit the

  signal piston in a direction such as the plunge

  pump can mate with the drive mechanism, and a discharge valve for controlling, in a stopping chamber, the fluid to which the piston assembly is exposed at least after the brake has been applied, the valve discharge valve is normally closed to enclose the fluid in the stop chamber to maintain the plunger assembly in a retracted position in which

  the pump plunger is disengaged from the drive mechanism

  and the discharge valve being movable to come to an open position in response to the slip signal to release fluid from the stopping chamber,

  after which the pump plunger can mate with the

canism of training.

  It follows, therefore, that the pump can not operate during all non-slip brake applications and that it only operates during relatively short periods of time in which skidding is being corrected, and the brakes

  are re-applied after skating correction.

  Provisions for pocketing the function

  of the pump and to ensure that there is no pumping of the fluid unless an automatic reapplication of the brake after a slip is necessary, have the advantage of reducing the amount of energy consumed to drive the pump and to avoid unnecessary use of the pump. Another advantage lies in the fact that the brake fluid can be used (unlike the conventional hydraulic fluid of the mineral type) while avoiding the degradation of its properties which would result if it were circulated.

continuously.

  Moreover, due to the presence of the signal piston, the pump's reciprocating movement does not

  not to vibrate a master cylinder to constitute the food

  tation. Otherwise this would be embarrassing if the master-

cylinder is small.

  In the retracted position, the signal piston is held against a stop and a spring can also act on the signal piston to solicit it

towards the stop.

  The fluid in the stopping chamber may act on the signal plunger at a second area opposite to the first, so as to keep the assembly in the retracted position. Alternatively, the pump plunger and the signal plunger are normally biased away from one another by a spring and the fluid in the stop chamber acts against complementary faces of the pump plunger and the plunger. signal piston to provide an opposing force

  the pressure acting on the first area.

  Preferably, a spring acts to urge the pump plunger to mate with the mechanism

  where permitted by following the movement

  The signal piston to the drive means.

  The drive mechanism conveniently comprises

  A camshaft can be driven by any suitable means, while the camshaft is supported in a body connected to a fluid reservoir. This has the advantage that there is no need for a seal

  sealing for the pump plunger.

  If the pump is associated with a modulator assembly and the cam shaft is driven by a wheel or from the vehicle transmission, a throttle is preferably included in the communication path between the stop chamber and the valve. discharge. This ensures that, if the rotation of the tree to

  cam is too fast - the pressure drop in

  This will cause the signal piston to move

  the pressure from the source of food

  to reduce the stroke of the plunger and hence the flow of the pump. At low speeds, the signal plunger will remain in the advanced position until the relief valve closes, and then the signal plunger

  will move to turn the pump off.

  If an electric motor is used to drive the cam shaft, a throttling is not

  indispensable, since the speed of rotation of the

  cam speed is predetermined. The electric motor can start whenever the brake is applied or

  when a skid signal is received.

  The modulator assembly may include a

  modulator piston normally maintained in a posi-

  advanced pressure by an expansion chamber

  to maintain an open kidney valve between the

  tion and brakes and the pressure in the expansion chamber is regulated by the discharge valve, with

  regulation of the pressure in the stop chamber.

  In another alternative arrangement, the separate modulating piston can be omitted and the signal piston itself also functions as a modulator piston to hold the brake valve open when in the retracted position and for

  allow the brake valve to close and

  to increase the effective volume of an expansion chamber defined in the bore between the signal piston and the brake valve and through

  from which the pressure coming from the food source

  tion is normally applied to the brake.

  Similarly, in an arrangement in which the discharge valve is placed between the power source and the brake and wherein the fluid is discharged from a flow path downstream of the discharge valve in the event of skating, the

  pump can be driven by a wheel, by the transmission

  vehicle or by an electric motor.

  The invention will be better explained and understood

  by the following description of two embodiments

  of the invention, given without limitation, with reference to the accompanying drawings in which s - Figure I-schematically shows a hydraulic anti-skid system for vehicle; - Figure 2, another anti-skid system for vehicle; FIG. 3 is a longitudinal section of a part of a modified modulator assembly that can be used in the braking systems of FIGS. 1 and 2; and FIG. 4, a section similar to that of FIG.

  of Figure 3 for another modulator assembly.

  In the braking system shown in FIG. 1, the speed sensors 1, 2 detect the speed of rotation of each of the front wheels which is braked by a brake 3, 4 and a single speed sensor detects the rotation speed of a rear axle 6 driving wheels which are braked by brakes

back 7.

  The signals from the speed sensors 1, 2 and 5 feed an electrical control module CM which analyzes the signals and outputs output voltages to excite three discharge electro-valves 8, 9 and 10.

  when the signal from one of the respective sensors equals

  slow 1, 2 or 5 indicates the possibility of skating.

  The discharge electro-valves 8, 9, 10 are incorporated in and form part of a modulator assembly 11. The modulator assembly 11 comprises a body 12 through which passes a transverse cam shaft 13 which can rotate through an electric motor or under the action of the gear boot. The camshaft 13 passes loosely into a bore 14 which is connected to a fluid reservoir 15. A pair of pump plungers 16 and 17 move in opposed holes 18 and 19 in the body 12. Each plunger 16, 17 is reciprocated in its bore 18, 19 by means of a cam eccentric 20 mounted on the shaft 13. A respective pump chamber 21, 22 is defined in each bore 18, 19 between the plunger 16, 17 and a wall 23, 24 located at the inner end of

each piercing 18, 19.

  A signal piston 25, 26 moves,

  in said body, in a bore 27, 28 which is

  The piston 25, 26 is connected to its respective plunger 16, 17 by means of a reduced diameter piston rod 29, 30, which is slidably guided through a joint. 31, 32 housed in the wall 23, 24. Each piston rod 29, 30 carries a wider head 33, 34 which is slidably housed in a bore 35, 36 formed in an adjacent end of the respective plunger 16, 17 where it is retained by a shoulder to form a connection

  empty motion. Each shoulder is normally

  puyé against the respective head 33, 34 by a spring 37,

  38 which acts between the plunger 16, 17 and the wall 23, 24.

  A spring 39 acts between the wall 23 and the signal piston 25, normally to urge the piston 25 to move away from the wall 23 and to come into

  a retracted position with support, at its outer end

  in this position the signal piston 25 keeps the pump plunger 16 away from the cam 20, so that the plunger 16 does not move.

can work.

  Similarly, a spring 41 acts between the wall 24 and the signal piston 26, normally

  to urge the piston 26 to move away from the wall -

  24 and coming in a retracted position of support, at its outer end, against a face of arrgt defined

  by a radial shoulder 42 located at an intermediate point

  In this position the signal piston 26 keeps the plunger 17 away from the cam 20, so that this plunger can not operate.

  Hydraulic pressure, coming from

  The pressure gauges, separated from a tandem master cylinder assembly 43 actuated via a booster, are adapted to control the operation of the brakes 3, 4 and 7. Specifically, the pressure from a pressure volume feeds each front wheel brake 3, 4

  by a non-return ball valve 44, 45 and this pressure

  sion also acts on the end of the signal piston which is remote from the cam 20 and cooperates with the stop face 40. From; similarly the pressure from the other pressure volume feeds the two rear wheel brakes 7 via a non-return ball valve 46 and this pressure also acts on the end of the signal piston 26 which is remote

  of the cam 20 and cooperates with the shoulder 42.

  The operation of each non-return valve 44, 45 is controlled by a modulator piston 47, 48, normally biased by a spring 49, 50 in

  a direction in which he maintains the valve respec-

  open. An expansion chamber 51, 52 is defined in a bore in which each piston 47, 48 moves on the side of the modulator piston 47, 48 which

  is respectively distant from the valve 44 or 45.

  the pump chamber 21 is connected to the two expansion chambers 51, 52 of the valves 44, 45 by a non-return valve 53 and a pair of non-return valves 54, 55 mounted downstream of the valve 53, so that a valve 54 or 55 leads to a respective expansion chamber 51, 52. A non-return valve 56 allows

  the flow of the reservoir 15 in the pump chamber 21.

  A throttle 57, 58 is located between

  each non-return valve 54, 55 and the expansion chamber

respectively 51, 52.

  A stop chamber 59, delimited in the bore 27 between the signal piston 25 and the wall 23, communicates with the pump chamber 21 by the non-return valve 53 and with the expansion chambers 51 and 52 by the valves. 54 and 55. Therefore, the signal piston 25 can be exposed, at its opposite ends, to the pressures existing in the master cylinder.

43 and in the Arrest Chamber 59.

  Each solenoid valve 8, 9 regulates the communication

  between a respective expansion chamber 51, 52

and the reservoir 15.

  The operation of the non-return valve

  46 is controlled by the signal piston 26 through

  median of a push rod 60.

  The pump chamber 22 is connected to a stop chamber 61 delimited, in the bore 28, between the piston 26 and the wall 24, via a non-return valve 62; a non-return valve 63 draws fluid from the reservoir 15 into the pump chamber 22. Therefore, the signal piston 26 can be exposed, at its opposite ends, to the pressures existing in the master cylinder 43 and in the chamber

Arrest 61.

  The solenoid valve 10 controls the communication

  between the stop chamber 61 and the reservoir 15.

  Springs 39 and 41 are respectively

  stronger than the springs 37 and 38.

  When the vehicle is in motion, the shaft 13 rotates and the two plungers 16 and 17 are normally spaced, under the effect of springs, the eccentric cam under the action of the signal pistons 25 and 26 as described above, so that the fluid does not flow. The modulator pistons 47 and 48 are held by the springs 49 and 50 against their stops, so that

  the valves 44, 45 are kept completely open.

  In a similar way the valve 46 is maintained completely

opened by the signal piston 26.

  When applying the brakes, the signal pistons 25, 26 are pushed towards the eccentric cam 20 by the fluid applied to the brake from the assembly

  of a master cylinder 43 which acts on the outer ends

  However, since fluid is enclosed in the stopping chambers 59 and 61, the plungers 16 and 17 are immersed in the stopping chambers 59 and 61. continue to be kept firmly away from the cam as stated above. If one of the front wheels slips, assuming, for example, that it is the wheel braked by the upper brake 3, the upper solenoid discharge valve 8

  by connecting the expansion chamber 51 and the chamber

  This operation causes the pressure in the wheel brake 3 to force the modulator piston 47 to move away from the valve 44 which it leaves.

  close. The continuation of the modular piston stroke

  47 in the same direction increases the volume of the brake and relieve the pressure applied to it. At the same time the signal piston 25 is forced, by the pressure from the master cylinder 43, to approach the eccentric cam 20. As a result, the plunger 16 can perform a back and forth motion to draw fluid of the reservoir 15 and push it back into the stop chamber 59 and into the expansion chamber 51, where it is brought back to the reservoir 15 by the valve of

open discharge 8.

  Nevertheless the reduction of the brake pressure allows the wheel to stop skating, so that the control module-CM removes the signal from

  slip and that the electro-discharge valve 8 closes.

  The modulator piston 47 is then forced to approach the ball valve 44 to reapply the brake and the signal piston 25 is urged to approach the abutment face 40 thereby retracting the plunger 16.

  to stop the operation of the pump.

  While the front wheel associated with the brake 3 is being corrected, the modulator piston 48 corresponds to the other front wheel brake 4 does not move because the non-return valve 55 remains closed. In a similar way the plunger 17 relating to the brakes of the rear wheels does not move. It follows therefore that each individual brake pressure can be

modified without affecting the others.

  The constrictions 57, 58 ensure that, if the rotation of the cam 20 is too fast, the pressure drop in the constrictions 57, 58 will cause the signal piston 25 to move against the pressure of the master cylinder 43 to reduce the diver's stroke

  16 and therefore its flow. If the cam 20 is

  born at constant speed, for example by an electric motor, then the restrictions 57 and 58 are not necessary. The signal piston 25 will be moved away from the stop 40 until finally the valve 8 or

  9 closes and the signal piston 25 can then move closer

  expensive stop 40 to put the pump out of service.

  If one of the rear wheels 7 or both slip, the electro-discharge valve 10 opens to

  relieve the pressure in the arrest chamber 61 at the

  see. This causes the pressure of the rear brakes 7 to push the signal piston 26 away from the valve 46 which can then close. Then the pressure enclosed in the ducts going to the rear wheel brakes is reduced by retracting the signal piston 26. This allows the plunger 17 to mate with the cam 20, whereby it can take a go-and-move movement. comes to draw fluid from the tank 15 and

  push him back into the detention room 61.

  Nevertheless, the reduction of the pressure of

  brake suppresses the skid signal, so that the

  3 dump valve 10 closes. The signal piston 26 is then forced away from the cam towards the stop shoulder 42, to initially pressurize the volume of fluid enclosed in the brake lines so as to reapply the brakes. rear wheels and then to reopen the valve 46. This movement of the signal piston 26 retracts the plunger relative to the cam 20 by putting the

pump out of order.

  Alternatively, the two rear brakes can be controlled separately as the front wheel brakes, but this requires the incorporation of an additional solenoid valve, an additional slip sensor and a pair of modulating pistons each of which will order a separate non-return brake valve. In the braking system of FIG. 2, each electro-discharge valve 8, 9, 10 is combined with a respective ball valve 44, 45 or 46, being adapted to control its operation; these valves act as cut-off valves and are arranged between respective flow ducts 70, 71 from respective pressure volumes of the master cylinder 43 and supply ducts 72, 73 and 74 ranging from

  the modulator assembly 11 to the brakes 3, 4 and 7.

  The non-return valves 56 and 63 are replaced

  placed by respective orifices 75 which go to the

  serving 15; the latter, in this embodiment, also serves the master cylinder 43 and is a part

  integral with the modulator assembly 11.

  A stop for the piston 26 is provided by

  a wall & the closed end of the bore 28.

  The conduits 77 and 78 leaving the tank provide recovery of the fluid in the pressure volumes of the maltre-cylinder 43 when the latter is

found in rest position.

  The discharge electro-valves 8, 9, 10 have the same construction, so that it suffices to describe one of them. As shown, each discharge valve 8, 9, 10 comprises a pin 80 integral with the movable cylindrical part 81 which is driven, in the position shown in the drawings, by a coil compression spring 82 supported against a radial flange 83 of the movable part 81. In this position the spindle 80 keeps the ball of the respective valve 44, 45, 46 away from its seat unlike

  the force of a return compression spring 84.

  The movable part 81 has a portion 85, remote from the spindle 80, which is slidably guided in a bore 86 of the body 12 and has an axial through hole 87 for balancing the pressure of the spool.

room 81.

  The piece 81 functions as a drawer or cylinder of a corresponding relief valve. A passage

  discharge 88 intersects the hole 86 and the relative position

  from step 89 of Exhibit 81, in relation to the

  discharge passage 88, controls the opening and closing

  placing of the discharge passage 88, during the axial movement of the workpiece 81 under the control of a solenoid coil whose excitation is controlled by the module of

CM command.

  When the master cylinder 43 is actuated, there is hydraulic fluid BoUs pressure in the stop chambers 59, 61 to maintain the plungers 16, 17 released from the eccentric cam 20. The excitation of the coil 90 of the valve 8 for example causes the closing of the valve 44 and the discharge of the fluid in the brake pipe 72 via the discharge passage 88 to the tank 15. As the pressure

  in the chamber containing the spring 82 falls, the pre-

  stress of the ball valve 54 is overcome by the pressure of the fluid enclosed in the stop chamber 59, so that fluid is expelled through the passage 88 from the chamber 59 under the effect of pressure

  in the master cylinder 43 acting on the piston 25.

  The movement of the piston 25 inwardly allows the spring 37 to move the plunger 16 inward to contact and "mate" with the eccentric cam 20. The plunger 16 will then take a

  movement back and forth under the action of the excenter cam

  20 and initially it will pump fluid from the reservoir port 75 through the valve 53 and the valve 54, then through the chamber containing the spring 82 and the

  discharge passage 88 by returning to the reservoir 15.

  Nevertheless, when the slippage signal is terminated in the control module CM, the coil 90 of the valve 44 will be de-energized to allow the moving part 81 to descend under the effect of the spring 82. As the pressure in the chamber containing the spring 82 is lower than that in the master cylinder 43, the cutoff member of the valve 44 will be held against its seat by the pressure difference and at the beginning pin 80 will not release its seat said member. Moving the workpiece 81 downward isolates the chamber containing the spring 82 from the discharge passage 88, so that fluid is then discharged by the pump plunger 16 into the brake pipe 72; the pressure in the conduit 72 and in the brake cylinder 3 is gradually increased by the reciprocating movement of the pump plunger 16. In most slip situations it will be necessary to reduce and increase the brake pressure several times. wheel before the control of skating has been mastered. Whenever a skating signal is produced in the module

  order CM the moving part 81 will rise to unload

  of the fluid of the brake duct 72. The coupling member

  pure valve 44 will remain in the closed position until the brake pressure reaches the pressure value established then in the master cylinder 43

  without a skid signal being issued.

  When the slippage situation is corrected and the pressure in the conduit 72 is increased, the pressure in the chamber 59 is also necessarily increased, so that the signal piston 25 moves to the right to retract the pump plunger 16. releasing it from the eccentric cam 20. The fluid under pressure in the chamber 59 is held by the ball valve 53 to keep the pump plunger 16 out of service until either of the sets of

  valve 8 or 9 is activated again.

  With the brakes released, the pressure in the chamber 59 disappears, but the spring 39 keeps

  still the signal piston 25 in its retracted position.

  It will be admitted that the operation of the valves

  9 and 10 when correcting a patient situation.

  on the right front wheel and the rear wheels is substantially identical to that of the valve 8. However, it should be noted that the pump plunger 16 serves one or both of the front wheels and that the excitation solenoid coils from either 8 or 9 valve assemblies will bring

  the pump plunger 16 in operation.

  According to a possible modification of the system of FIG. 2, the control module CM will be arranged

  in order to produce two levels of coil excitation

  90. In a first excitation stage, a small current flows into the respective coil so as to produce a sufficient movement of the movable part 81 so as to close the cut-off element of the valve 44, 45 or 46,

  but retaining the closed discharge passages 88.

  This will result in a maintenance period during

  where the brake pressure is kept constant.

  It has been recognized that it is desirable to have such a holding period under certain circumstances to allow the electronic unit to distinguish between a true skating situation and deceleration.

  momentary of a wheel, caused by a bump in the road.

  If the ON control module decides, during the hold period, that there is in fact an imminent skidding situation, the current flowing in the coil will then have to be increased to produce the complete displacement of the moving part 81 so that at

  open the associated relief passage 88.

  The construction and operation of the system of Figure 2 are also the same as

  those of Figure 1 and reference marks have been used.

  to designate the counterparts.

  In the modified modulator assembly shown in FIG. 3, for example for controlling

  the operation of the rear wheel brakes in the system

  In FIG. 1, the plunger 17 has a stepped contour and a portion 100 adjacent to its largest diameter inner end moves in a bore 101 in the adjacent end of the signal plunger 26. has a fairly long length. A spring 102 acts between a closure 103 of the inner end of the bore 28 and the adjacent inner end of the signal piston 26 to hold the latter in the retracted position in contact with a

  stopper formed by a closure 104 of the outer end

  In this position a radial shoulder 105 provided on the signal piston 26 contacts a shoulder 106 in line with the diameter variation of the pump plunger 17, also to hold the plunger 17 in the retracted position, coupling with the cam 20, so as to put the

pump out of order.

  The non-return valve 63 is housed in the pump plunger 17 to enable fluid to be withdrawn into the pump chamber 107 situated between the plunger 17 and the signal piston 26, during a suction stroke of the pump, and the non-return valve 62 is placed between the pump chamber 107 and the chamber

stop 61.

  The signal piston 26 also has a

  turn, so that when the chamber of ar-

  rtt 61 is pressurized by the pump during

  application of the brake, for example after the

  slippage, the pressure in the stopping chamber 61 acts on a net area sufficient to overcome the force generated by the brake pressure 7, which also acts on the first area of the signal piston 26,

  namely the area of the outermost end 108.

  With this arrangement, apart from the discharge valve 10, all the constituent elements of a modulator assembly are disposed within a single longitudinal bore having stepped portions whose diameters grow towards the outer end at larger diameter closed by the closure 104. This facilitates the manufacture and

mounting.

  The construction and operation of the modulator assembly of FIG. 3 are also the same as those of FIG. 1 and corresponding markers have been used to designate the counterparts. In the modulator assembly of FIG. 4, the portion 100 of the largest diameter plunger 17 also moves in the bore 28 and the signal plunger 26 has a reduced diameter leading head 109 which moves in a bore made in an extension 111 of the outer end adjacent pump plunger 17. A radial passage 113 formed in the extension 111 allows free communication between the bore 110 and the stop chamber 61. The spring 41 surrounds the extension 111 and acts between the plunger 17 and the signal plunger 26, normally to hold the plunger 17 and the signal plunger 26 in a distended position, in which the extension head 109 is in contact with a radial shoulder 112 of the extension 111. The spring 102 acts to hold the plunger 17 and the plunger

  26 in their retracted positions.

  The valve 63 is disposed in the wall or body surrounding the bore 28, between the reservoir

  and the pump plunger 17, and the valve 62 is

  The stopper 61 is defined between the piston 26 and the plunger 17, and the pump chamber 107 at the inner end of the plunger 17, at the same end as the valve 63 of FIG.

drilling 28.

  In the position shown, in which the discharge valve is closed and the brakes 7 are

  normally applied by the master cylinder 43, the pressure

  fluid flow on a brake 7 acts on the area 108 of the piston 26 to put the fluid under pressure in the stop chamber 61 located between the plunger 17 and the piston 26. This pressure acts on a net effective area to generate a reaction force holding the piston 26 and hence the plunger 17 in

their retracted positions.

  When slip occurs, the discharge valve 10 is opened to discharge the fluid from the stop chamber 61, so that the brake pressure acting on the area 108 urges the piston 26 to

  move to the cam 20 allowing at the beginning the

  setting the valve 46, then increasing the volume of the brake to release the brake pressure. The spring 41 is stronger than the spring 102, so that the plunger 17 moves with the piston 26 until the plunger 17 comes into contact with the cam 20. Thereafter the continuation of the movement of the piston 26 compresses the spring 41 to allow a further reduction of the brake pressure and the plunger 17 reciprocates under the effect of the cam 20 in the bore 28, unlike the force of the spring 41. The movement of the plunger 17 to the outside of the bore 28 draws fluid from the reservoir 15 into the pump chamber 107 through the valve 63 and the plunger movement inwardly flushes the fluid from the pump chamber 107 through of the valve 62 in the stop chamber 61, from which it returns to the reservoir 15 via the open discharge valve 10. As long as the discharge valve 10 is open, the movement of the plunger 17 is absorbed by the spring 41, so that the movement

  piston 26 is of low amplitude.

  When the slippage has been corrected, the relief valve closes to lock fluid in the stowed chamber 61, which prevents relative movement

  of the plunger 17 and the piston 26 towards each other. nevertheless

  less the brake pressure acting on the area 108 puts the fluid under pressure in the pump chamber 107 at a pressure level higher than that existing in the stop chamber 61, because the area 108 is larger than the effective annular area of the chamber 107. Thus, during the subsequent inward movement of the plunger 17,

  the fluid is expelled from the pump chamber 107 in the chan-

  stance 61 in which it acts to displace

  the piston 26 away from the plunger 17

  in order to increase the volume of the stopping chamber.

  During the subsequent movement of the plunger 17 outwards, the piston 26 moves with the plunger 17 to reduce the brake volume and increase the brake pressure to a value greater than that which existed at the beginning of the brake. previous race. Thus the brake pressure is increased sawtooth, decreasing slightly during each stroke of the pump, but increasing a relatively larger amount during each stroke of admission, up to that the piston 26 and the plunger 17 reach their retracted positions, so that the valve 46 is open to allow the pressure of the

  master cylinder to continue the reapplication of the brakes.

  The arrangement and operation of the modulator assembly of FIG. 4 are also the same as those of FIG.

  corresponding benchmarks to designate homogeneous

logue s.

Claims (21)

REVENDIOATIONS   1. Anti-hydraulic brake system   skating for vehicles, wherein the supply of operating fluid of a vehicle brake from a power source is modulated according to   the slip signals provided by a detecting means   slipping apparatus, characterized in that the system comprises a pump having a piston assembly, which includes a pump plunger (16, 17) which can reciprocate in a bore by means of a mechanism for driving (13, 20), a signal piston (25, 26) coupled to the pump plunger (16, 17) and resilient means (39, 41, 102) for biasing the pump plunger (16, 17). ) to disengage from the drive mechanism (16, 20), the signal piston (25, 26) having a first surface exposed to the pressure of the power source (43) or the   brake (3, 7) when the brake is applied to   refer to the signal plunger (25, 26) in a direction such that the pump plunger (16, 17) can mate with the drive mechanism (13, 20), and a discharge valve (8, 9, 10). ) for controlling the fluid, contained in a stop chamber (59, 61), to which the piston assembly is exposed at least after the brake has been   applied, the discharge valve (8, 9, 10) being normal-   closed to enclose the fluid in the fluid stop chamber (59, 61) to hold the piston assembly in a retracted position in which the pump plunger (16, 17) is disengaged from the drive mechanism ( 13, 20) and this discharge valve   (8, 9, 10) can be brought into a position of   in response to the slippage signal for releasing the fluid from the stopping chamber (59, 61), after which the plunger (16, 17) can mate with the mechanism drive (13, 20).   System according to claim 1, characterized in that the signal piston (25, 26) is held against a stop (40, 42) and that a spring (39, 41) acts on the signal piston (25). , 26) to solicit it   to approach the stop (40, 42).   3. System according to claim 1 or 2, characterized in that the fluid in the stopping chamber (59, 61) acts on the signal piston (25, 26) by a second area opposite to the first,   to keep the assembly in the retracted position.   System according to claim 1 or 2, characterized in that the pump plunger (16, 17) and the signal plunger (25, 26) are normally biased away from each other by a spring ( 37, 38) and that the fluid in the stopping chamber (59, 61) acts on complementary faces of the pump plunger (16, 17) and the signal plunger (25, 26) to provide a force opposition to the pressure acting on the first area.   5. System according to one of the claims   preceding, characterized in that the pump plunger (16, 17) and the signal plunger (25, 26) move in different bores (18, 19) and (27, 28) and are coupled together by an extension ( 29, 30) moving through an existing partition between the holes.   6. System according to one of the claims   I to 5, characterized in that the pump plunger (17) moves in a bore (101) formed in the piston signal (26).   7. System according to one of claims 1   to 5, characterized in that the pump plunger (17) and the signal plunger (26) both move in piercing.commun (28).   8. System according to claim 6 or 7,   characterized in that a spring (41) acts between the pump plunger (17) and the signal plunger (26), normally to solicit & deviate.   9. Seolon system one of the claims   previous, characterized in that opposing non-return valves (53, 56; 62, 63) are arranged between a fluid reservoir (15) and the stopping chamber (59, 61) and between the chamber stop (59, 61) and the reservoir (15).   10. System according to claim 9, characterized   in that one of the non-return valves (62, 63)   is housed in the pump plunger (17).   11. System according to claim 9, wherein   in that one of the non-return valves (62, 63) is accommodated in the pump plunger (17) and in that the other non-return valve is housed in the piston signal (26).   12. System according to one of the claims   characterized in that a spring (37, 38) acts to urge the pump plunger (16, 17) to mate with the drive mechanism (13, 20) when this is allowed as a result of the movement. piston   signal (25, 26) approaching the drive mechanism. (13, 20).   13. System according to one of the claims   preceding, characterized in that the mechanism of   trainement comprises a camshaft (13) which seats   in a body (12) connected to the reservoir (15) of the fluid.   14. System according to claim 13,   in that the pump is associated with a modulator assembly (1il) and in that the camshaft (13) is driven by a wheel or by the transmission of the vehicle, a throttle (5 ?, 58) being included in a communication channel between the stopping chamber (59) and the discharge valve (8, 9).   15. System according to claim 14, characterized in that the modulator assembly (11)   comprises a modulator piston (47, 48) which is normally   maintained in a position advanced by the pressure in an expansion chamber (51, 52) to maintain tc a brake valve (44, 45) open between the supply and the brakes and that the pressure in the chamber d expansion (51, 52) is controlled by the discharge valve (8, 9) with pressure regulation in the stop chamber (59).   16. System according to claim 14, characterized   characterized in that the signal piston (26) itself acts as a modulating piston to hold the brake valve (46) open when in a retracted position and to allow the brake valve (46) to close and subsequently increase the useful volume   an expansion chamber which is delimited in the   connecting the signal piston (26) and the brake valve (46) and through which the pressure from   the power supply is normally applied to the brake.   17. System according to one of the claims   1 to 13, characterized in that the discharge valve (8, 9, 10) is arranged between the supply source   (43) and the brake (3, 4, 7) and that the fluid   from a communication path downstream of the discharge valve is discharged in case of slippage, being pumped back by the pump to reapply the brake at the end of slippage.   18. System according to one of the claims   previous ones, characterized in that at least two   pump generators (16, 17) are driven by a common drive mechanism (13, 20), each plunger being   associated with a single signal piston.   19. System according to claim 18, characterized   in that one of the plungers (16) is adapted to control the supply of the working fluid to the brakes (3, 4) on the front wheels of a vehicle and in that   the other plunger (17) is adapted to control the food   actuation fluid to the brakes (7) on the rear wheels of the vehicle.   20. System according to claim 19, characterized   characterized in that said plunger (16) is arranged to control the operation of the brake (3) on a front wheel independently of the operation of the brake (4) on the other front wheel.   21. System according to one of the claims   18 to 20, characterized in that the stop chamber (59) of one (25) of the signal pistons of a pair controls the pressurization of the expansion chambers (51, 52) of a pair modulator pistons (47, 48) and in that the modulator pistons control the supply of pressurized fluid from the supply source to different front wheel brakes of the vehicle, the other signal piston (26) -Also acting as a modulating piston for modulating the pressurized fluid from the power source to the brakes on the rear wheels of the vehicle, the arrangement being such that during normal braking the drive mechanism (13, 20) will operate freely, but if one of the brakes emits a slip signal the appropriate pump plunger (16, 17) will be reciprocated by the drive mechanism (13, 20). ) for controlling the respective modulating piston, the other modulator piston remaining in its retracted position e while its expansion chamber is isolated from the stop chamber by a non-return valve, the other diver pump not affected.